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FORM 160.47-NOM3
YORK INTERNATIONAL
SECTION 2
OPERATION
BASIC DESCRIPTION
The York YS Chiller package uses a refrigerant-flooded
evaporator and a liquid-cooled condenser. The compres-
sor is a heavy-duty, industrial-rated rotary screw com-
pressor. The package consists of four major components.
Refer to the Chiller Package Component drawing, Fig-
ure 14.
COMPONENTS
DRIVELINE
The driveline is made up of the compressor and a heavy
duty industrial induction motor. The motor is mounted to
the compressor with a “D”-flange spacer. The “D”-
flange eliminates the necessity to align the motor and
compressor.
The compressor is a positive displacement, variable vol-
ume, direct drive, twin helical rotary screw compressor.
The male rotor is a direct drive by the motor; the female
rotor is an idler that is driven by the male rotor. The
rotors do not touch each other or the compressor hous-
ing. The rotors are separated by a hydraulic oil seal,
which prevents high pressure gas from leaking into low
pressure areas.
Evaporator pressure gas is drawn into the compressor
and compressed by the male and female rotors as they
rotate together and reduce the volume of gas.
The compressor bearings are industrial duty rated, anti-
friction rolling element bearings. No sleeve bearings are
used. Oil is injected into the compressor by differential
pressure to lubricate the bearings, seal the rotors and
remove the heat of compression. The oil that is injected
into the compressor mixes with the compressed gas and
is separated from the refrigerant gas in the oil separa-
tor.
A slide valve is positioned between the male and female
rotors, that moves axially to match the compressor ca-
pacity to that of the evaporator refrigeration load. The
slide valve is moved by differential pressure. As the
slide valve moves toward the unloaded position, less suc-
tion gas is pumped through the compressor. The control
panel automatically positions the slide valve to match
the load requirements. The slide valve can be operated
manually. When the compressor is shut off, a spring
returns the slide valve to unloaded position. The com-
pressor starts with the slide valve in the unloaded posi-
tion.
OIL SEPARATOR
The oil separator removes the oil that was injected into
the compressor. The oil separator is a three stage de-
sign. Most of the oil separates by a reduction in velocity
in the first stage. The discharge gas is then directed
through a high surface area that collects more of the
oil. The final stage is a coalescer element(s) that re-
moves the fine aerosol particles of oil.
The oil separator is very efficient and removes nearly
100% of the oil. The very small amount of oil that does
pass through the oil separator is returned to the com-
pressor through a filter driers.
The oil separator is also a reservoir for the oil. A tem-
perature controlled immersion heater is installed in the
oil reservoir. The oil heater is interlocked with a low oil
level safety switch.
CONDENSER
Oil free refrigerant gas leaving the oil separator flows
into the condenser. Water flowing through the condenser
removes the heat of compression and condenses the
refrigerant gas into refrigerant liquid.
The liquid refrigerant then flows through the integral
liquid sub-cooler located in the bottom of the condenser.
The sub-cooled liquid refrigerant flows into the evapo-
rator by deferential pressure.
EVAPORATOR
Condensing pressure refrigerant flows out of the liquid
sub-cooler into the liquid line where the liquid refriger-
ant is metered into the evaporator by an orifice. The
liquid refrigerant begins to flash (and cool) after flow-
ing through the orifice plate. The refrigerant is distrib-
uted in the bottom of the evaporator. Liquid refrigerant
floods the evaporator and the heat is exchanged from
the evaporator liquid, flowing on the inside of the evapo-
rator tubes, to the liquid refrigerant on the outside of the
tubes.
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